This type of mixing of typography is quite popular in many forms of media today. I’ve noticed that the restaurant A&W actually uses this a lot. Each line is a different font style with the more important words being in a larger font. It also appears to create a nice book end effect with the words Future and Tomorrow in the same or similar font. To create visual interest, some lines are enhanced with shapes or flourishes. It is these extra little bits that make this poster stand out more than pure text posters would.